Curable organopolysiloxane composition useful for coating optical fibers

ABSTRACT

The present invention provides curable silicone compositions, comprising: 
     (a) a substantially linear olefinic group-containing polydiorganosiloxane; 
     (b) a resinous olefinic group-containing polysiloxane; 
     (c) a reactive organic monomer; 
     (d) an organohydrogenpolysiloxane, and 
     (e) a hydrosilation catalyst. 
     There are also provided articles of manufacture prepared by coating substrates such as optical fibers with said composition as well as methods for making said curable compositions and articles of manufacture.

BACKGROUND OF THE INVENTION

The present invention relates to optical fibers coated with novelsilicone compositions. More particularly, the present invention relatesto optical fibers having a silicone cladding or protective coatingthereon, said silicone composition comprising the reaction product of asilicone fluid, a silicone resin, and a reactive organic monomer such asan alpha olefin.

The emerging field of light wave telecommunications make use of light totransmit information through a transparent medium in a way comparable totransmitting electricity through a copper wire. The advantage of suchoptical telecommunications over the presently employed electromagneticsystems is that is has the potential to accommodate thousands of timesmore communications traffic than radio communications.

Since the discovery of lasers the only technical obstacle to lightwavecommunications over great distances has been the development of asuitable transmission medium. Air, for example, although penetrable bylight, is unsuitable because rain, fog and other atmospheric conditionscan weaken the light signal. Development of the glass fiber lightguide,or optical fiber, provided an excellent and relatively inexpensivetransmission medium.

Modern optical fibers typically consist of a core of high transparencysilica glass which transmits the light surrounded by a protective orcladding layer. Such protective coatings not only insulate the opticalfiber from the environment, but also act as an internal mirrorreflecting the light back into the core, thus preventing loss of thelight signal outside the optical path.

In the production of fiber optics cable for telecommunications, thematerial used as the protective layer must be very flexible, not adheretoo closely to the glass fiber core, and maintain its integrity andoptical characteristics in changing environments, including temperaturecycles of from -50° C. to 80° C. It is also desirable that theprotective layer be easily strippable so that the integrity of the fibercan readily be checked.

The prior art discloses various silicone compositions which areexpressly said to be suitable as a coating composition for opticalfibers, and silicone compositions which do not refer to theirsuitability for such use, typically because they were invented beforethe present optical fiber technology was developed.

Included in the first class is Suzuki, U.S. Pat. No. 4,380,367, whichdiscloses a coating for optical fibers, comprising:

(a) 100 parts by weight of a vinyl group terminatedmethylphenylpolysiloxane having a viscosity at 25° C. of 100 to 15,000centipoise and with a methyl/phenyl molar ratio of from 1/1 to 10/1;

(b) an organohydrogenpolysiloxane selected frommethylhydrogenpolysiloxanes having a viscosity at 25° C. of from 0.7 to5000 centipoise and containing at least three silicon-bonded hydrogenatoms per molecule, and methylphenylhydrogenpolysiloxanes having aviscosity at 25° C. of 0.7 to 5000 centipoise and containing at leastthree silicon-bonded hydrogen atoms per molecule, with a methyl/phenylmolar ratio not smaller than 1/1, the amount of (b) being an amountwhich provides a molar ratio of silicon-bonded hydrogen atoms in (b) tosilicon-bonded vinyl groups in (a) which ranges from 0.8/1 to 10/1; and

(c) 0.5 to 1000 ppm precious metal or precious metal containinghydrosilation catalyst, as precious metal based on the total amount of(a) and (b).

Included in the latter class is Dallavia, U.S. patent application Ser.No. 538,093, filed Oct. 3, 1983, now U.S. Pat. No. 4,526,953, andincorporated by reference into the present disclosure. Dallaviadiscloses curable silicone compositions particularly suitable as releasecoating compositions which comprise:

(a) an addition curable diorganopolysiloxane base polymer having up toabout 20 percent by weight alkenyl functional groups and having aviscosity of from about 50 centipoise to about 100,000 centipoise at 25°C.;

(b) an SiH-containing polysiloxane crosslinking agent having up to 100percent by weight SiH-containing siloxy groups and having a viscosity inthe range of 15 centipoise to 1000 centipoise at 25° C.; (c) aneffective amount of precious metal or precious metal containing catalystto promote an addition cure hydrosilation reaction between said basepolymer and said crosslinking agent; and

(d) an amount of α-olefin or mixture of α-olefins having up to about 30carbon atoms effective to enhance said addition cure.

Nelson, U.S. Pat. No. 3,284,406, discloses a composition consistingessentially of:

(a) a polysiloxane of the formula ##STR1## where R and R¹ are phenyl ormethyl and at least 80 mol percent of the R¹ groups are methyl, saidpolysiloxane having a viscosity of from 500 to 500,000 centipoise at 25°C.;

(b) from 5 to 50 percent by weight based on the weight of (a) and (b) ofa copolymer of SiO₂ units, (CH₃)₃ SiO₀.5 units and (CH₃)₂ (CH₂═CH)SiO₀.5 units, wherein there is from 1.5 to 3.5 weight percent vinylgroups based on the weight of (b), and the ratio of (CH₃)₂ (CH₂═CH)SiO₀.5 units to SiO₂ units is from 0.6:1 to 1:1;

(c) a compound compatible with (a) and (b) which is a siloxanecontaining from 0.1 to 1.7 percent by weight silicon-bonded hydrogenatoms, the remaining valences of the silicon atoms in (c) beingsatisfied by methyl or phenyl radicals, there being at least threesilicon-bonded hydrogen atoms per molecule, and the amount of (c) beingsuch that there is from 0.75 mol of SiH per mol of vinyl radicals in (a)and (b); and

(d) a platinum catalyst.

Modic, U.S. Pat. No. 3,436,366, discloses a composition comprising:

(a) a vinyl chainstopped polysiloxane having a viscosity of from 50,000to 750,000 centipoise at 25° C.,

(b) an organopolysiloxane copolymer comprising trimethylsiloxane units,methylvinylsiloxane units and SiO₂ units, where from about 2.5 to 10mole percent of the silicon atoms contain silicon-bonded vinyl groupsand where the ratio of trimethylsiloxane units to SiO₂ units is from0.5:1 to 1:1;

(c) a platinum catalyst and

(d) an organohydrogenpolysiloxane crosslinking agent.

It has now been discovered that protective coatings for optical fiberscan be prepared from curable silicone compositions, comprising:

(a) a substantially linear olefinic group-containingpolydiorganosiloxane;

(b) a resinous olefinic group-containing polysiloxane;

(c) a reactive organic monomer;

(d) an organohydrogenpolysiloxane crosslinking agent; and

(e) an effective amount of precious metal or precious metal containinghydrosilation catalyst.

SUMMARY OF THE INVENTION

It is one object of the present invention to provide curable siliconecompositions useful as protective cladding for optical fibers.

It is another object of the present invention to provide curablesilicone compositions which can be applied to optical fibers at highspeeds substantially free of bubbles and which cure rapidly uponexposure to elevated temperatures.

Another object of the present invention is to provide optical fiberscoated with novel silicone compositions.

Still another object of the present invention is to provide methods formaking novel curable silicone compositions and optical fibers coatedwith said novel curable silicone compositions.

These and other objects are accomplished herein by a curable siliconecomposition, comprising:

(a) a substantially linear olefinic group-containingpolydiorganosiloxane;

(b) a resinous olefinic group-containing polysiloxane;

(c) a reactive organic monomer;

(d) an organohydrogenpolysiloxane crosslinking agent; and

(e) an effective amount of precious metal or precious metal containinghydrosilation catalyst.

DESCRIPTION OF THE INVENTION

In accordance with one aspect of the present invention there is provideda curable silicone composition, comprising:

(a) a substantially linear olefinic group-containingpolydiorganosiloxane;

(b) a resinous olefinic group-containing polysiloxane;

(c) a reactive organic monomer;

(d) an organohydrogenpolysiloxane crosslinking agent; and

(e) an effective amount of precious metal or precious metal containinghydrosilation catalyst.

In accordance with another aspect of the present invention there isprovided a method for making coated optical fibers, comprising:

I. applying to a core fiber of high transparency silica glass a curablesilicone composition, comprising:

(a) a substantially linear olefinic group-containingpolydiorganosiloxane;

(b) a resinous olefinic group-containing polysiloxane;

(c) a reactive organic monomer;

(d) an organohydrogenpolysiloxane crosslinking agent; and

(e) an effective amount of precious metal or precious metal containinghydrosilation catalyst; and

II. exposing the coated core fiber of high transparency silica glass toan elevated temperature for an amount of time sufficient to cure saidsilicone composition to said core fiber of high transparency silicaglass.

Component (a) of the curable silicone composition of the presentinvention can be any silicone polymer known in the art which containsthe requisite olefinic groups. Generally, component (a) is analkenyl-terminated polydiorganosiloxane having the general formula##STR2## where each R¹ is an independently selected monovalentsubstituted or unsubstituted, saturated or unsaturated hydrocarbonradical, R² is an alkenyl radical, preferably vinyl or allyl, and n is anumber sufficient to provide a viscosity of from about 10 centipoise toabout 5,000,000 centipoise at 25° C. Preferably, the R¹ groups aremethyl radicals or a mixture of methyl and phenyl radicals, and,preferably, the viscosity ranges from about 100 centipoise to about1,000,000 centipoise at 25° C. More preferably, the viscosity rangesfrom about 1000 centipoise to about 250,000 centipoise at 25° C. The R²radicals, in addition to vinyl and allyl, can be any aliphaticallyunsaturated radicals which are capable of reacting with silicon-bondedhydrogen atoms and includes, for example, butenyl, hexenyl, octenyl,butynyl, pentynyl, and the like. Of course, there may be utilizedmixtures of various olefin-containing polydiorganosiloxanes in thepractice of the present invention. Those of ordinary skill in the artwill be able to ascertain other suitable olefinic group-containingpolydiorganosiloxanes without undue experimentation.

Component (b) of the present invention can be any resinous, olefinicgroup-containing polysiloxane known in the art. Preferably, siliconeresin (b) is an MQ or MDQ resin having from about 1.5 to about 10 molpercent of siloxy units containing silicon bonded alkenyl groups.Preferably, such alkenyl groups are vinyl or allyl and most preferablyare vinyl units. It should be noted that in the MDQ resins the alkenylgroups can be bonded to either or both of the monofunctional anddifunctional siloxy units, however, it is preferable that only thedifunctional siloxy units contain the alkenyl groups.

In both the MQ and MDQ resins the organo groups which are not alkenylgroups can be any hydrocarbon groups free of aliphatic unsaturation.Most preferably, such groups are methyl or phenyl or a mixture thereof.

In practicing the present invention there is typically employed fromabout 50 to about 400 parts by weight of resin or mixture of such resinsper 100 parts by weight of component (a). Preferably there is utilizedfrom about 150 to about 250 parts by weight of resinous olefinicgroup-containing polysiloxane (b) per 100 parts by weight ofpolydiorganosiloxane (a). Of course, more or less silicone resin may beused for applications other than coating optical fibers withoutdeparting from the spirit of the invention or the scope of the appendedclaims.

Generally, the various types of siloxane units in component (b) areselected so that the ratio of M units to Q units is from about 0.5:1 toabout 1:1. Additionally, the D units are normally not present in anamount exceeding 10 mole percent of the total number of siloxy units.

The resins of component (b) typically are solid resinous materials andmost often are commercially available as a solution in a solvent such astoluene or xylene, for example, as a 40 to 70 percent by weightsolution. For ease of handling, component (b) can be dissolved in someor all of olefin-containing polysiloxane (a) and the solvent strippedfrom the resulting solution to produce a solution of component (b) incomponent (a).

Component (c) of the present invention includes all organic monomerswhich are capable of reacting with the hydrogen atoms of component (d).Such reactive organic monomers are often referred to in the art asreactive diluents.

The preferred reactive monomers for practicing the present invention areα-olefins of the type described in U.S. patent application Ser. No.538,093 (Dallavia), filed Oct. 3, 1983, now U.S. Pat. No. 4,526,953, andincorporated herein by reference. Generally, such α-olefins arestraight-chain hydrocarbons which contain a terminal double bond and maybe characterized by the general formula

    CH.sub.3 (CH.sub.2).sub.x --CH═CH.sub.2

where x is an integer from 1 to about 30. The only limiting factor inpractice is that as x increases beyond 30, the solubility of theα-olefin in the silicone components decreases. Preferably x ranges fromabout 13 to about 27.

These α-olefins possess a number of properties which make themparticularly suitable for use in silicone compositions used as claddingfor optical fibers. The α-olefins impart many of the advantageousproperties of organic compositions to the silicone; thus, for example,the silicone component does not require that phenyl groups be present inorder to obtain the necessary refractive index. Such α-olefins are alsosubstantially less expensive than silicones, thereby reducing theoverall cost of the curable composition and the optical fiber coatedtherewith. These α-olefins can be added directly to the siliconecomponents to a level of about 40 percent by weight withoutsignificantly affecting the cure or properties of the siliconecomponents.

The high reactivity of the terminal double bond of the α-olefins inprecious metal catalyzed addition reactions allows them to be used inapplications where very rapid curing is essential. The volatility ofα-olefins varies greatly depending upon the molecular weight, however,for the preferred C₁₆ to C₃₀ α-olefins flash points range from about132° C. to about 265° C. It is also noteworthy that α-olefins have beenshown to have little or no toxic effect except where extensivelyinhaled; oral and dermal LD₅₀ values are in excess of 10 grams/kg, andskin and eye irritation are minimal. This combination of costeffectiveness, silicone solubility, cure compatibility, low volatilityand low toxicity make α-olefins excellent modifiers for the presentinvention.

Preferably, the reactive organic monomers are present in an amountranging from about 0.5 to about 25 percent by weight based on the weightof components (a) and (b). More preferably, the reactive organic monomeris present in an amount ranging from about 2.5 to about 20 percent byweight and, most preferably, is present in an amount of from about 5 toabout 15 percent by weight based on the weight of components (a) and(b).

Other suitable reactive organic monomers can be readily ascertained bythe artisan without undue experimentation and includes, for example,compositions such as Chemlink 2000, an acrylated α,ω C₁₂ -C₁₄ aliphaticdiol available from Santomer Corporation.

Component (d) can be any organohydrogenpolysiloxane known in the art,and can be a linear organohydrogen fluid, a resinousorganohydrogenpolysiloxane, or a mixture thereof. Generally, theorganohydrogenpolysiloxane crosslinking agents useful in the presentinvention contain an average of at least three silicon-bonded hydrogenatoms per molecule. The remaining valences of the silicon atoms aresatisfied by oxygen atoms. The organohydrogenpolysiloxanes can behomopolymers, copolymers and mixtures thereof which contain unitsselected from, for example, dimethyl siloxane units,methylhydrogensiloxane units, dimethylhydrogensiloxane units,trimethylsiloxane units and SiO₂ units. Some specific examples oforganohydrogenpolysiloxanes include polymethylhydrogensiloxane cyclics;copolymers of trimethylsiloxy and methylhydrogensiloxy units; copolymersof dimethylhydrogensiloxy units and methylhydrogensiloxy units;copolymers of trimethylsiloxy, dimethylsiloxy and methylhydrogensiloxyunits; and copolymers of dimethylhydrogensiloxy, dimethylsiloxy andmethylhydrogensiloxy units.

The amount of organohydrogenpolysiloxane present is generally an amountsufficient to provide from about 0.8 to about 3 silicon-bonded hydrogenatoms per alkenyl radical in components (a), (b) and (c).

Component (e) is a precious metal or precious metal-containing catalysteffective for initiating or promoting a hydrosilation cure reaction(referred to hereinafter simply as a precious metal catalyst orhydrosilation catalyst). The precious metal catalyst used in thepractice of the present invention includes all of the well knownplatinum and rhodium catalysts which are effective for catalyzing thereaction between silicon-bonded hydrogen atoms and alkenyl radicals.These materials especially include the platinum hydrocarbon complexesdescribed in U.S. Pat. Nos. 3,159,601 and 3,159,662 to Ashby, and theplatinum alcoholate catalysts described in U.S. Pat. No. 3,220,970 toLamoreaux, as well as the platinum catalysts of U.S. Pat. No. 3,814,730to Karstedt. Additionally, the platinum chloride-olefin complexesdescribed in U.S. Pat. No. 3,516,946 to Modic are useful herein. All ofthe aforesaid patents relating to suitable catalysts are incorporated byreference into the present disclosure.

Other suitable hydrosilation catalysts are well known in the art and canbe, for example, complexes of the metals ruthenium, palladium, osmiumand iridium.

Typically, the amount of hydrosilation catalyst employed ranges fromabout 1 ppm to about 500 ppm, as precious metal, based on the totalweight of the composition. Preferably, the amount of precious metalcatalyst is from about 10 to about 150 ppm, as precious metal, based onthe weight of components (a), (b) and (c).

Additional ingredients may be added to the curable compositionsdescribed herein to lend specific properties and to allow thecompositions to be tailored to the user's needs. Illustrative ofcommonly included additional ingredients are cure inhibitors, forexample, as described in U.S. Pat. No. 4,256,870 to Eckberg and vinylgum cure accelerators such as those described in U.S. Pat. No. 4,340,647to Eckberg. Other conventional additives are also intended to be withinthe scope of the appended claims.

Although the compositions of the present invention can be prepared bymerely mixing the various components together in a suitable manner, itis usually most convenient to prepare these compositions in two or moreseparate packages which are combined at the time the composition is tobe applied and cured to the optical fiber.

In the case of a two package formulation it is preferable that onepackage include the substantially linear olefinic group-containingpolydiorganosiloxane (a), the resinous olefinic group-containingpolysiloxane (b), the reactive organic monomer (c) and the preciousmetal catalyst (e). The second package contains as its sole essentialingredient organohydrogenpolysiloxane (d), but as a matter ofconvenience, the second package also contains a portion of at least oneof components (a), (b) and (c). Those skilled in the art are familiarwith such two package systems, hence, a detailed discussion is notnecessary. It is noteworthy, however, that an especially suitablemulticomponent packaging system can be derived from the teachings ofU.S. Pat. No. 4,448,415 to Eckberg, which is incorporated herein byreference.

Application of the curable silicone coating composition of the presentinvention to an optical communication glass fiber can be carried out byany method known in the art, for example, dipping or spraying. Curing isnormally effected by passing the coated optical fiber through an ovenmaintained at a temperature of from about 200° C. to about 900° C. for aperiod ranging from about 0.1 to about 5 seconds.

In order that those skilled in the art might be better able to practicethe present invention, the following examples are provided by way ofillustration and not by way of limitation. All parts are by weightunless otherwise stated.

EXAMPLES EXAMPLE 1

To a one liter three neck flask equipped with a mechanical stirrer,vacuum take off adapter, 75° angle adapter (head), condensor,thermometer, receiving flask and thermal controller there was added 400grams of a trimethylsiloxy-methylvinylsiloxy-tetrasiloxy resin (e.g.MD^(vi) Q) as 60% solids in xylene and 160 grams of vinyl terminatedpolydimethylsiloxane having a viscosity of about 3500 centipoise at 25°C. The contents of the flask were than heated to 150° C. at 30 mm Hg.The solvent was collected in the receiving flask leaving a clearstripped liquid polydimethylsiloxane fluid containing the MD^(vi) Qresin. The viscosity of this material was greater than 2 millioncentipoise at 25° C. The resin to polymer ratio, on a mole basis, was60:40. To 100 grams of the fluid-resin solution there was added 10 gramsof Chemlink 2000 (an acrylated α, ω C₁₂ -C₁₄ aliphatic diol fromSantomer Corp.). The acrylate was dispersed by warming the mixture to50° C. and blending. The resultant liquid was readily pourable. Therewas then added 0.92% by weight of platinum complexed with methylvinyltetramer as catalyst (Karstedt) and 0.92% by weight of dimethylmaleateinhibitor.

EXAMPLE 2

To 38 grams of the silicone resin solution prepared in Example 1 therewas added 2 grams of a mixed C₁₆ -C₁₈ α-olefin (Gulf Oil ChemicalsCompany). The mixture was blended until a uniform solution having aviscosity of 28,850 centipoise at 25° C. was obtained. One percent byweight of platinum catalyst (Karstedt) was also added to the solutionand blended therein.

EXAMPLE 3

To 190 grams of the silicone resin solution prepared in Example 1 therewas added 10 grams of mixed C₁₆ -C₁₈ α-olefin, 2 grams of platinumcatalyst (Karstedt) and 2 grams dimethylmaleate inhibitor. The solutionwas blended until uniform and the viscosity was found to be 9150centipoise at 25° C.

EXAMPLE 4

To a one liter three neck flask equipped as in Example 1 there was added460 grams of the same MD^(vi) Q resin and 225 grams of the same vinylterminated polydimethylsiloxane. The siloxane resin solution wasstripped under vacuum to remove the solvent. The resin to fluid ratio ona molar basis was 55:45, respectively. To this solution there was thenadded 0.4 grams platinum catalyst (Lamoreaux) and 3 gramsdimethylmaleate inhibitor. Once the polymer was blended to disperse bothcatalyst and inhibitor, the polymer was maintained under 30 mm Hg vacuumat 60°-65° C. for thirty minutes. The resultant material had a viscosityof 32,800 centipoise at 25° C. To 254 grams of the thus preparedmaterial was added 2.5 grams of dimethylmaleate inhibitor and 2.5 gramsplatinum catalyst (Karstedt). The resin to polymer ratio, on a molebasis, was 55:45.

EXAMPLE 5

To a one liter three neck flask equipped as in Example 1 there was added457 grams of the same MD^(vi) Q resin, 223 grams of the same vinylterminated polydimethylsiloxane, and 25 grams of mixed C₁₆ -C₁₈α-olefin. The resin, fluid and reactive diluent were blended untiluniform and then stripped to 150° C. at 25 mm Hg to remove the solventof the MD^(vi) Q resin. Thereafter, 3.5 grams platinum catalyst(Karstedt) and 1.9 grams dimethylmaleate were added and the materialblended until uniform. The resultant material had a viscosity of 16,700centipoise at 25° C. The resin to polymer ratio, on a mole basis, was55:45.

EXAMPLE 6

To a one liter three neck flask equipped as in Example 1 there was added426 grams of the same MD^(vi) Q resin, 255 grams of the same vinylterminated polydimethylsiloxane, and 25 grams of mixed C₁₆ -C₁₈α-olefin. The resin, fluid and diluent were blended until uniform, thenstripped to 150° C. at 25 mm Hg to remove solvent contained in theMD^(vi) Q resin. Thereafter, 3.5 grams of platinum catalyst (Karstedt)and 1.9 grams of dimethylmaleate were added. The resultant material hada viscosity of 5800 centipoise at 25° C. The resin to polymer ratio was,on a mole basis, 50:50.

EXAMPLE 7

To a one liter three neck flask equipped as in Example 1 there was added404 grams of the same VD^(vi) Q resin, 270 grams of the same vinylterminated polydimethylsiloxane, and 27 grams of mixed C₁₆ -C₁₈α-olefin. The resin, fluid and diluent were blended until uniform, andthen stripped to 150° C. at 25 mm Hg to remove the solvent of theMD^(vi) Q resin. Thereafter, 3.5 grams of platinum catalyst (Karstedt)and 1.9 grams dimethylmaleate inhibitor were added. The resultantmaterial had a viscosity of 10,050 centipoise at 25° C. The resin topolymer ratio, on a mole basis, was 45:55.

EXAMPLE 8

To 11.1 grams of the material prepared in Example 1 there was added 1.2grams of hydride containing MQ resin. The catalyzed polymer was cast ona metal sheet and cured at 150° C. Tensile strength, elongation andhardness were measured according to standard test procedures and theresults are set forth in Table I.

EXAMPLE 9

To 10 grams of the material prepared in Example 2 there was added 0.7grams of hydride containing MQ resin. The catalyzed polymer was cast ona metal sheet and cured at 150° C. Tensile strength, elongation andhardness were measured according to standard test procedures and theresults are set forth in Table I.

EXAMPLE 10

To 20 grams of the material prepared in Example 3 there was added 2grams of hydride containing MQ resin. The catalyzed polymer was cast ina Teflon® mold and cured at 150° C. Tensile strength, elongation andhardness were measured according to standard test procedures and theresults are set forth in Table I.

EXAMPLE 11

To 20 grams of the material prepared in Example 4 there was added 2grams of hydride containing MQ resin. The catalyzed polymer was cast ina Teflon® mold and cured at 150° C. Tensile strength, elongation andhardness were measured according to standard test procedures and theresults are set forth in Table I.

EXAMPLE 12

To 30 grams of the material prepared in Example 5 there was added 1.5grams of trimethyl stopped methylhydrogenpolysiloxane having a viscosityof about 25 centipoise at 25° C. The catalyzed polymer was cast in aTeflon® mold and cured at 150° C. Tensile strength, elongation andhardness were measured according to standard test procedures and theresults are set forth in Table I.

EXAMPLE 13

To 30 grams of the material prepared in Example 6 there was added 1.5grams of trimethyl stopped methylhydrogenpolysiloxane having a viscosityof about 25 centipoise at 25° C. The catalyzed polymer was cast in aTeflon® mold and cured at 150° C. Tensile strength, elongation andhardness were measured according to standard test procedures and theresults are set forth in Table I.

EXAMPLES 14 AND 15

To 30 grams of the material prepared in Example 7 there was added 3grams of hydride containing MQ resin and 1.5 grams of trimethylendstopped methylhydrogenpolysiloxane (Examples 14 and 15,respectively). The catalyzed polymer was cast in a Teflon® mold andcured at 150° C. Tensile strength, elongation and hardness were measuredaccording to standard test procedures and the results are set forth inTable I.

                  TABLE I    ______________________________________    Example           Tensile (psi)                      Elongation (%)                                  Hardness (Shore A)    ______________________________________     8     781        100         72     9     580        100         62    10     785        100         74    11     481         60         82    12     1113       100         69    13     1270       120         64    14     828        100         59    15     875        100         61    ______________________________________

The foregoing examples show that the addition of reactive diluents suchas mixed C₁₆ -C₁₈ α-olefins and Chemlink 2000 provides curable polymerswhich are easily pourable at room temperature. In order to obtain adurometer (hardness) in the 60 to 80 range, the level of MD^(vi) Q resinhas to be greater than about 25% by weight.

All of the foregoing examples cured rapidly, had a satisfactory potlife, had acceptable physical characteristics, and were easily strippedfrom fiber glass. Such compositions are also likely to be well suitedfor use as paper release compositions.

We claim:
 1. A curable composition, comprising:(a) 100 parts by weightof a substantially linear olefinic group-containingpolydiorganosiloxane; (b) from about 50 to about 400 parts by weight ofa resinous olefinic group-containing polysiloxane per 100 parts byweight of component (a); (c) from about 0.5 to about 25 percent byweight based on the weight of components (a) and (b) of an organicmonomer capable of reacting with the hydrogen atoms of component (d);(d) an organohydrogenpolysiloxane crosslinking agent in an amountsufficient to provide from about 0.8 to about 3 silicon-bonded hydrogenatoms per alkenyl radical in components (a), (b) and (c); and (e) aneffective amount of precious metal or precious metal containinghydrosilation catalyst.
 2. A curable composition as in claim 1, whereinthe olefinic group-containing polydiorganosiloxane has the generalformula ##STR3## where each R¹ is an independently selected monovalentsubstituted or unsubstituted, saturated or unsaturated hydrocarbonradical, R² is an alkenyl radical, and n is a number sufficient toprovide a viscosity of from about 10 centipoise to about 5,000,000centipoise at 25° C.
 3. A curable composition as in claim 2, wherein theR² radicals are vinyl or allyl radicals.
 4. A curable composition as inclaim 2, wherein the viscosity ranges from about 100 centipoise to about1,000,000 centipoise at 25° C.
 5. A curable composition as in claim 3,wherein the viscosity ranges from about 1000 centipoise to about 250,000centipoise at 25° C.
 6. A curable composition as in claim 1, wherein theresinous olefinic group-containing polysiloxane is an MQ resin or an MDQresin.
 7. A curable composition as in claim 6, wherein the resin hasfrom about 1.5 to about 10 mole percent of siloxy units containingsilicon-bonded alkenyl groups.
 8. A curable composition as in claim 2,wherein there is from about 150 to about 250 parts by weight of MQ orMDQ resin per 100 parts by weight of olefinic group-containingpolydiorganosiloxane.
 9. A curable composition as in claim 1, whereinthe organic monomer is an α-olefin.
 10. A curable composition as inclaim 9, wherein the α-olefin has the general formula

    CH.sub.3 (CH.sub.2).sub.x --CH═CH.sub.2

where x is an integer from 1 to about
 30. 11. A curable composition asin claim 10, wherein the value of x is from about 13 to about
 27. 12. Acurable composition as in claim 9, wherein the α-olefin is present in anamount of from about 2.5 to about 20 percent by weight based on theweight of compoennts (a) and (b).
 13. A curable composition as in claim9, wherein the α-olefin is present in an amount of from about 5 to about15 percent by weight based on the weight of components (a) and (b). 14.A curable composition as in claim 1, wherein the organic monomer is anacrylated α, ω aliphatic diol.
 15. A curable composition as in claim 9,wherein the organohydrogenpolysiloxane is a silicone resin.
 16. Acurable composition as in claim 9, wherein theorganohydrogenpolysiloxane is a silicone fluid.
 17. A curablecomposition as in claim 1, wherein the components are provided in atleast two separate packages.
 18. A method for making a curablecomposition, comprising:I. mixing: (a) 100 parts by weight of asubstantially linear olefinic group-containing polydiorganosiloxane; (b)from about 50 to about 400 parts by weight of a resinous olefinicgroup-containing polysiloxane per 100 parts by weight of component (a);(c) from about 0.5 to about 25 percent by weight based on the weight ofcomponents (a) and (b) of an organic monomer capable of reacting withthe hydrogen atoms of component (d); (d) an organohydrogenpolysiloxanecrosslinking agent in an amount sufficient to provide from about 0.8 toabout 3 silicon-bonded hydrogen atoms per alkenyl radical in components(a), (b) and (c); and (e) an effective amount of precious metal orprecious metal containing hydrosilation catalyst.